JPH09245827A - Manufacture of alkaline storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To heighten the coefficient of use of an active material using only a slight amount of a conductive auxiliary agent by aging nickel hydroxide at a prescribed temperature for a prescribed time before initial charging. SOLUTION: This battery comprises a cathode produced by uniting, drying and pressure molding spherical nickel hydroxide, which is mixed with a fine nickel hydroxide particles, with a metal porous supporting body, an anode, a separator, and an alkaline electrolytic solution. Before the initial charging of the battery after assembly, the battery is left still at 40-80 deg.C for 24 hours or longer, so that the fine nickel hydroxide particles are aged. The fine nickel hydroxide is converted into one having a crystal structure easy to be charged and discharged by the aging. Consequently, electricity quantity of the fine active material particles with which spaces of active material particles and gaps between the active material and a core material are filled can be sufficiently drawn out, so that a high coefficient of use is provided by using only a slight amount of the added conductive agent (e.g. cobalt compound).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing an alkaline storage battery using a nickel positive electrode, which can be used for a nickel-cadmium storage battery, a nickel-hydrogen storage battery, a nickel-zinc storage battery and the like.

[0002]

2. Description of the Related Art As a positive electrode for an alkaline storage battery, a positive electrode using nickel hydroxide as an active material has been conventionally used.

This nickel hydroxide positive electrode is "sintered"
And "non-sintered" electrode plates. The "sintered" electrode plate is mainly used in batteries for power tools that require a large current because of its good current collecting performance. On the other hand, the "non-sintered" electrode plate is obtained by integrating the active material itself with the metal porous support, and it is possible to obtain a larger capacity than the "sintered" electrode plate. It is mainly used as a type of battery.

In order to improve the packing density of the active material,
Generally spherical ones are used. This spherical nickel hydroxide grows by stirring particles (primary particles) obtained by dropping an ammonia complex of nickel into an aqueous solution of sodium hydroxide in an alkali, and secondary particles that are aggregates of primary particles. It is obtained by making it into particles. The nickel ammonia complex is promptly converted into nickel hydroxide by the alkali, but at this time, the cation of the alkali, water, an anion species in the nickel salt and the like are incorporated into the crystal. The presence of these impurities in the crystal deteriorates the characteristics as a battery material. Therefore, when producing nickel hydroxide, impurities are removed by leaving it in a high-temperature, high-concentration alkali, which is generally called "aging".

With this technique, the packing density was improved and the capacity was further increased as compared with the case where amorphous nickel hydroxide was used.

However, it is generally said that this "non-sintered" electrode plate cannot use up the theoretical capacity of the active material unless various additives are added. As the additive, compounds such as zinc, cobalt, cadmium, nickel metal, carbon and the like are used. Zinc, cadmium and the like are used for the purpose of suppressing the production of γ-nickel oxyhydroxide during overcharge. Also, metallic nickel,
Carbon and the like are often used as a conductive aid for improving the current collecting property in the electrode plate.

Cobalt compounds are often used as conductive aids, and attempts have been made to improve the efficiency by covering the surface of the active material with finer powder. Further, the cobalt compound is dissolved in the alkaline electrolyte in the battery and is oxidized and deposited at a potential lower than that of nickel hydroxide charged at the time of initial charging. The deposited high-order cobalt compound forms a conductive film and contributes to the improvement of the utilization rate of the active material. In addition, it is said that the battery with a cobalt compound added to the positive electrode will improve the utilization rate if left at room temperature or high temperature for about one day before the first charge and discharge. This is the time taken to dissolve and diffuse the cobalt compound. Is taken as.

Further, in such a positive electrode, a binder or a thickener is generally used in order to prevent the active material from falling off in the battery and prevent the capacity from being reduced by the cycle. As such a binder and a thickener, an organic compound having almost no conductivity is generally used, and it is clear that the utilization rate is lowered. As a means for suppressing such a drop of the active material, there is known a technique of converting an electrode plate containing a salt of the active material into an active material with an alkaline aqueous solution (Japanese Patent Publication No. 7-60).
681). However, this technique is effective in removing the active material in the battery, but is not sufficient because the active material drops out when the nickel salt is made into the active material with an alkali and when washed with water.

[0009]

Further, when a battery using these positive electrodes is stored at a high temperature for a long period of time in a discharged state, a change in the positive electrode potential causes a high-order cobalt which is considered to be stable in a normal battery. There is a problem in that the compound is eluted, the conductive film is destroyed, the utilization factor changes greatly before and after storage, and a good utilization factor cannot be obtained after storage.

Further, as with the cobalt compound, the same can be said for metallic nickel, carbon, etc., which are mentioned as the conduction aid, but the conduction aid needs to sufficiently cover the surface of the active material, so that fine particles are formed. It must be used in a highly dispersed state. However, since the fine particles have a large specific surface area, they cause a decrease in packing density.

Therefore, the present invention improves the utilization rate by using a small amount of a conductive auxiliary agent, avoids the decrease in conductivity due to the elution of the conductive auxiliary agent into the electrolytic solution, and suppresses the decrease in the utilization rate after storage. The purpose is to improve the packing density of the active material and further to prevent the active material from falling off during these treatments.

[0012]

In order to solve the above-mentioned problems, the present invention was stored at 40 to 80 ° C. for 24 hours or more before the first charging / discharging after the battery was constructed to make it an active material outside or inside the battery. The fine nickel hydroxide particles are aged by the alkaline electrolyte in the battery.

By this aging, a good utilization factor of the active material can be obtained by using a very small amount of the conductive additive, a decrease in the utilization factor due to the elution of the conductive additive can be avoided, and the packing density can be further improved. Further, the dropout of the active material when converting the salt into the active material can be suppressed by converting the nickel salt into the active material in the battery.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention is obtained by integrating spherical nickel hydroxide obtained by mixing a porous metal support and fine nickel hydroxide particles, and drying and pressing. The obtained positive electrode was used to age fine nickel hydroxide particles in an alkaline electrolyte in a battery, and a good utilization rate can be obtained by using a small amount of a conductive auxiliary agent.

Further, in the invention according to claim 2, an electrode plate obtained by integrating a metal porous support and nickel hydroxide, drying and press-molding is impregnated with a solution containing a nickel salt, After drying, the battery is constructed, the nickel salt is made into an active material with the alkaline electrolyte in the battery, and the battery is left at high temperature before the first charge and discharge to age the particles that have been made into the active material. It is possible to prevent the active material from falling off at the stage of converting the nickel salt into an active material.

Further, according to the invention described in claim 3, a battery is constituted by an electrode plate obtained by integrating nickel hydroxide prepared by mixing a metal porous support and a metal salt mixture containing a nickel salt, The nickel salt is made into an active material with the alkaline electrolyte inside, and the battery is left at high temperature before the first charge and discharge to age the particles that have been made into an active material. It is possible to prevent the active material from falling off.

The aging of nickel hydroxide in the battery according to the present invention is fundamentally different from the elution and diffusion of the cobalt compound, and is used for a battery using a conventional cobalt compound in an amount of 5% by weight or more. By removing impurities in the fine nickel hydroxide crystals that are not present, the fine nickel hydroxide is converted into a crystal structure that is easy to charge and discharge. This makes it possible to sufficiently draw out the amount of electricity of the fine active material particles filling the voids between the active material particles and between the active material and the core material, thus improving the utilization rate of the active material.

[0018]

Next, specific examples of the present invention will be described.

Example 1 Spherical nickel hydroxide having an average particle size of 10 μm (Ni: Co: Zn = 100: 1.5: 4.
0) 100 parts and 2 mol / l of nickel sulfate hexahydrate
An aqueous solution of sodium hydroxide having a concentration of 23% by weight was added dropwise to the aqueous solution, and 5 parts of infinitely fine nickel hydroxide powder obtained by stirring was mixed in a dry state, and pure water was added at 20% by weight to prepare a paste. . The obtained paste was filled in a foaming nickel substrate, dried at 80 ° C. for 30 minutes, and pressure-molded to 3
A positive electrode plate having a theoretical capacity of 1800 mAh was produced by cutting into 6.5 mm × 110 mm × 0.70 mm. The packing density at this time was 640 mAh / cc.

The positive electrode plate thus obtained was again dried at 80 ° C. for 30 minutes to form a battery group together with the hydrogen storage alloy negative electrode via the sulfonated polypropylene separator, which was then housed in an outer container and then hydroxylated with a specific gravity of 1.30. 40g / l for potassium
2.32 ml of an electrolytic solution in which lithium hydroxide was dissolved was poured to form a sealed nickel-hydrogen storage battery having a positive electrode theoretical capacity of 1800 mAh of 4/5 A size. This battery was left standing at 45 ° C. for 3 days to age fine nickel hydroxide particles before the initial charge and discharge. The battery thus obtained is referred to as Battery A of the present invention. Also, before the first charge and discharge, 40 ℃
The battery A ′ was left for 24 hours.

(Example 2) A positive electrode obtained in the same manner as the battery A was immersed in a 2 mol / l nickel sulfate aqueous solution, and the temperature was changed to 80 ° C.
Was dried for 30 minutes, and in consideration of the increase in capacity due to the conversion of nickel sulfate into the active material, a positive electrode plate was prepared so as to have a current of 1800 mAh. The electrode plate size at this time is 36.5 mm.
× 105 mm × 0.67 mm, the packing density is 70
It was 0 mAh / cc. Using this positive electrode plate, a 1800 mAh battery was constructed in the same manner as in Example 1 above, and allowed to stand at 45 ° C. for 3 days before the first charge / discharge to age fine powder of nickel hydroxide.

The battery thus obtained was designated as Battery B of the present invention. Further, a battery B ′ was left at 40 ° C. for 24 hours before the first charge / discharge.

(Embodiment 3) Spherical nickel hydroxide (Ni: Co: Zn = 100: 1.5: 4.
0) Add 100 parts of nickel sulfate to 20% by weight of pure water.
Prepare a paste by adding 5 parts of melted material, and take into account the increase due to the conversion of nickel sulfate into the active material, 1800 mAh
The positive electrode of was produced. The electrode plate size at this time is 36.5 m.
m × 110 mm × 0.73 mm, and the packing density at this time was 614 mAh / cc. Battery A using this
A 1800 mAh battery was constructed in the same manner as described above, and the fine powder of nickel hydroxide was aged for 3 days at 45 ° C. before the first charge and discharge.

The battery thus obtained was designated as Battery C of the present invention. A battery C ′ was left at 40 ° C. for 24 hours before the first charge / discharge.

Furthermore, spherical nickel hydroxide (Ni: C
(o: Zn = 100: 1.5: 4.0) 100 parts of cobalt hydroxide 7 parts, cobalt oxide 3 parts and zinc oxide 2 parts are mixed, pure water is added to form a paste, and then metal porous. Filled into a support, dried, pressure molded, 110 mm x 3
A 6.5 mm × 0.78 mm electrode plate was prepared. Using this, a 1800 mAh battery was constructed in the same manner as the battery A, and used as a comparative example. The packing density at this time is 575 mAh
/ Cc.

It is apparent that the electrode plate of the comparative example to which the conductive additive and other additives are added has a lower packing density than the batteries A, B and C.

The batteries A, A ', B, B', obtained as above,
C, C'and comparative example, 0.1 CmA, 150 at 20 ℃
%, And discharged at a final voltage of 0.8 V at 0.2 CmA to obtain the initial charge / discharge. Then, the battery was left at 45 ° C. for 3 days, charged and discharged under the same conditions as the initial charge and discharge, and the battery capacity was determined. The ratio with the theoretical capacity of 289 mAh per 1 g of nickel hydroxide was defined as the positive electrode utilization rate, which is shown in the table in Evaluation 1.

Further, for the batteries A, B and C and the comparative example, the charging conditions were also 0.1 CmA and 150% at 20 ° C.
And the discharge current was 0.5 and 1.0 CmA, respectively, and the evaluation was performed, and 0.5 CmA discharge was evaluated as 2,1.0 CmA.
The discharge was rated as 3, and the positive electrode utilization rate is shown in Table 1 as in the case of the rating 1.

In addition, the batteries A, B and C and the comparative example were charged at 1.0 CmA and 120% at 20 ° C.
At 0.8 ° C, the final voltage was 0.8 V, discharge was performed, the utilization factor was measured, and the evaluation was set to 4. Then, the sample was left at 65 ° C for 30 days,
After that, the same measurement as the evaluation 4 was performed to obtain the evaluation 5, and these are also shown in Table 1.

[0030]

[Table 1]

Evaluation 1 shows that the utilization rates of the batteries A, B and C exceed 95%, which is clear to be equivalent to the comparative example using a large amount of the conductive auxiliary agent. It can be said that a good utilization rate was obtained. This is presumably because impurities such as potassium ions, sulfate ions, water molecules in fine nickel hydroxide crystals were removed by the aging before the initial charge / discharge, and the crystal form was changed to be easy to charge / discharge.

However, in the batteries A ', B'and C'where the aging of the fine nickel hydroxide particles was not sufficient, the utilization rates were generally lower than those in the batteries A, B and C. This indicates that the aging of the fine nickel hydroxide in the battery is not sufficient and that aging for at least 24 hours or more is necessary. The ambient temperature needs to be at least 40 ° C. or higher in order to sufficiently perform the aging, while it is preferably 80 ° C. or lower in order to protect the separator and the like.

From the results of Evaluation 2 and Evaluation 3, it was revealed that the capacity was reduced even when the discharge current was changed, as in the comparative example.

It is presumed that these are because the gaps between the active materials were filled with the fine active material during the discharge, so that the proton diffusion between the active materials was smoothly performed and the electrochemical reaction resistance was reduced. To be done. Another reason is that the current density between the core material and the active material has decreased due to the increase in the contact area between the core material and the active material.

The utilization factor in the evaluation 4 was almost the same as that in the evaluation 3, but in the comparative example in the evaluation 5, the utilization factor was greatly decreased. On the other hand, in the batteries A, B and C, there was almost no decrease in the utilization factor even in the evaluation 5, and the values were almost the same as those in the evaluation 4.

In the comparative example, the electroconductivity aid was so much eluted into the electrolytic solution that the electron conduction between the positive electrode active materials was impaired, and voids were generated at the places occupied by the electroconductivity aid. It is presumed that this is because the electron conduction and the proton diffusion were hindered. On the other hand, since the batteries A, B, and C do not contain a conductive auxiliary agent, voids are not generated during storage and the conductivity between the active materials is not changed, so that the structure of the positive electrode is not changed. It is considered that the usage rate was small because the structure was very small and the structure was the same as before storage.

Further, the positive electrode plates obtained in the same manner as the batteries B and C were immersed in a potassium hydroxide solution (specific gravity 1.3) at 60 ° C., then washed with water and dried to prepare a battery. When the test of Evaluation 1 was conducted in the same manner as the batteries B and C, the capacity was about 7% smaller, and the alkaline treatment outside the battery resulted in the loss of the active material than the alkaline treatment inside the battery of the present invention. There were many.

The spherical nickel hydroxide used in the present invention may be composed of nickel hydroxide alone, but cobalt (0.1 to 5% by weight), zinc (0.1 to 8% by weight). %), Cadmium (0.1 to 5% by weight), and the like, more preferably containing at least one internal additive within the above range. The average particle size of 5 to 25 μm is good because the active material is less likely to fall off. If the particle size is smaller than this, the packing density is low, and if the particle size is large, the active material is likely to fall off. Further, nickel hydroxide as an additive preferably has an average particle size of 3 μm or less, and a particle size larger than this does not sufficiently function. Further, in the present invention, a nickel salt solution is used as the immersion liquid. As such nickel salts, inorganic nickel salts such as nickel sulfate, nickel nitrate and nickel halide, and organic nickel salts such as nickel acetate and nickel citrate are used. As a solvent for these salts, water or an organic solvent such as alcohol or acetone can be used alone or in an appropriate mixture. These substances can also be used as a solvent when preparing a paste.

Further, in the present invention, no conductive auxiliary agent is used, but it goes without saying that a better utilization rate can be obtained by adding the conductive auxiliary agent. As the conductive aid, there are cobalt compounds such as cobalt hydroxide, cobalt oxide, and metallic cobalt, nickel powder, carbon powder, etc., and it is possible to add up to 20% by weight of nickel hydroxide.
Addition of about 3% by weight makes the utilization rate 100%. Further, as a method of adding these substances, in addition to a method of mixing with a conventional active material paste, a salt that functions as a conduction aid by changing with an alkali, such as cobalt sulfate,
If it is an inorganic cobalt salt such as cobalt nitrate, by mixing with the nickel salt of the present invention or by using alone instead of the nickel salt, the surface of the active material can be coated more efficiently than before, and a decrease in packing density due to addition can be avoided. It's easy to guess what you can do.

[0040]

As described above, in the present invention, the voids in the electrode plate are filled with the fine particles obtained by converting the active material salt into an active material outside or inside the battery to remove the alkaline electrolyte in the battery. By aging it, the adhesion between the active materials and between the active material and the core material is increased, and the current density is reduced, so that it is possible to obtain the effect that the utilization rate is improved without using the conductive additive as much as possible. . Moreover, the use of the conductive auxiliary agent as little as possible suppresses the structural change of the positive electrode before and after the storage, and minimizes the change in the utilization rate before and after the storage.

Further, by using the alkaline electrolyte in the battery for converting the active material salt into an active material, it is possible to reduce the conventional steps of alkali treatment, washing and drying, which is industrially effective.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideo Kaitani 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. Spherical nickel hydroxide having an average particle size of 5 to 25 μm, nickel hydroxide particles having an average particle size of 3 μm or less, and at least one selected from metallic cobalt, cobalt oxide or cobalt hydroxide. A battery is composed of a positive electrode holding a paste mixed with an additive containing 0.1 to 3% by weight in terms of metallic cobalt on a metal porous support, a negative electrode, a separator and an alkaline electrolyte, and before the first charge and discharge thereof. A method for producing an alkaline storage battery, which comprises leaving at a temperature of 40 ° C. or higher and 80 ° C. or lower for at least 24 hours or longer. 2. An additive containing spherical nickel hydroxide having an average particle diameter of 5 to 25 μm and at least one selected from metallic cobalt, cobalt oxide or cobalt hydroxide in an amount of 0.1 to 3% by weight in terms of metallic cobalt. After holding the paste mixed with the metal porous support, drying and pressure molding,
A positive electrode is obtained by impregnating an aqueous metal salt solution containing at least a nickel salt and then drying it to form a battery with a negative electrode, a separator, and an alkaline electrolyte. A method for producing an alkaline storage battery, which is characterized by leaving it under at least 24 hours or more. 3. An additive containing 0.1 to 3% by weight in terms of metallic cobalt of at least one selected from spherical nickel hydroxide having an average particle diameter of 5 to 25 μm and metallic cobalt, cobalt oxide or cobalt hydroxide. An aqueous solution of a metal salt containing at least a nickel salt is added to a mixture of the above to form a paste, which is integrated with a metal porous support and dried, and a pressure-molded positive electrode, a negative electrode, and a separator to form a battery,
A method for producing an alkaline storage battery, which comprises leaving this battery at 40 ° C. or higher and 80 ° C. or lower for at least 24 hours or more before initial charge / discharge.